Experimental Research On The Influence Of Plastic Deformation On Stress Corrosion Cracking Of304Austenitic Stainless Steel

Plastic deformation is prevalent in the molding process of austenitic stainless steels. After plastic deformation, material’s strength and hardness increase, plasticity and toughness decrease, which results in a significant impact on the stress corrosion resistance. Stress corrosion cracking is the commonest failure form of austenitic stainless steel, with the features of high corrosion speed and severe damage, which will cause catastrophic damage to the equipments and companies. In addition, it is more often that corrosion damage happens in the area of large plastic deformation firstly. Therefore, for the sake of equipments’stable operation, it has a very important practical significance to study the effect of plastic deformation on the stress corrosion resistance of304stainless steels.304stainless steels were tensile deformed with different deformation rates and deformation amounts. The microstructure and martensite content of samples after deformation were measured by metallographic microscope, hardness tester and XRD, in order to study the effect of deformation rates and deformation amounts on performance of304stainless steels. Through the stress corrosion test of slow strain rate, the influence of plastic deformation on304stainless steels was studied. Main research results are summarized as follows:(1) The results of optical microscopy and micro-hardness test showed that, after plastic deformation, the samples produced deformation-induced martensite transformation. The volume fraction of martensite increased as the amount of plastic deformation increased, and the growth rates was fast firstly and then slow. When the deformation amount was less than30%, the martensite content increased faster; when the deformation amount was more than30%, the growth rate obviously slowed down.(2) Comparing the XRD data and hardness of different deformation rates samples, in the same amount of plastic deformation, slow tensile specimen (0.5mm/min) produced more martensite than the rapid one (5mm/min); the hardness was also higher than the former. (3) Through the slow rate test of deformed samples in3.5%NaCl solution, it was showed that as plastic deformation amounts increased, the stress corrosion susceptibility of304stainless steels showed increasing trend as a whole. When the deformation amount was less than30%, the stress corrosion susceptibility increased obviously with the increasing of deformation; when the deformation amounts reached to30%, the growth rate of susceptibility index slowed down. In the same amount of plastic deformation, the stress corrosion susceptibility of slow tensile samples was higher than the fast ones.(4) The effect of plastic deformation on of stress corrosion sensitivity of304stainless steels was due to martensite transformation. Along with the deformation increased, the deformation-induced marten site content raised, resulting in the increasing of stress corrosion sensitivity.(5) The mechanical properties and stress corrosion sensitivity of deformed samples before and after solution treatment were compared. Solution treatment could reduce the martensite content of plastic deformed304stainless steels, so that the resistance of stress corrosion was improved. Besides, when the deformation amount was larger than30%, although improving, the stress corrosion tendency still existed.